1. Field of the Invention
The present invention relates to a resin-coated metal plate and drawn cans using these plates. More specifically, the invention relates to resin-coated metal that has been laminated with special layers of resin film, and drawn cans using these resin-coated metal plates.
2. Prior Art
Conventionally, drawn cans have widely been used, which have been processed by drawing metal plates such as tin-plated steel or aluminum plates (hereinafter “DR can”).
For these kinds of DR cans, the inner surface side of the can has been formed with resin-film layers, in order to prevent degradation in flavor and a deterioration of the contents due to metal elution from the metal plate, and the occurrence of pinholes and so forth.
The above-mentioned resin film, together with being required to have superior workability in conformity with draw-processing, it is also required to have superior adherence so as to prevent peeling from the steel plate. Moreover, this resin film is required to have superior shock-resistance, in order to tolerate the shock of stamping, canning and transport.
In order to improve workability and adherence, the resin film should not have a very high degree of hardness. If the degree of hardness is too high, it will be low in workability and adherence, and because it is also too brittle it will be low in shock-resistance as well.
On the other hand, although print and varnish are applied to the outer surface side of the can. After printing and varnishing, it undergoes a drying process in a baking oven and so forth. Therefore, at the inner surface side of the can, where varnishing and printing have not been applied, cases can occur where there is scarring (wicket scars) at the holding of the plate of the can.
In order to prevent these wicket scars from becoming the starting point of corrosion during the filling of the contents, due the negative influence they have on the corrosion resistance of the can body, these cans are formed using a resin-coated metal plate. In addition to becoming the starting point of corrosion, these wicket scars also affect the flavor of the contents in beverages and so forth (flavor degradation).
One problem with wicket scarring in this kind of can body, where the corrosion resistance and flavor and so forth have been degraded, is that the softer the resin film is the easier it is for this to occur.